Watches That Stop
It is assumed that the watches in question have been cleaned, that they are generally in good order with special reference to properly fitted staffs, pallet arbors and jewels, etc. All escapements are of the double roller type unless otherwise mentioned.
Drop locks - correct
Guard freedom - excessive
Corner freedom - correct
In this example, the guard freedom was greater than the corner freedom. When the curve test was tried, the roller jewel would catch on the tips of the fork. The repair consisted of flattening the end of the guard finger. For this purpose a punch should be ground so that the end will fit between the horns of the fork. A very light tap with a small hammer will do the work. After flattening the guard finger, the sides were stoned to provide the necessary guard freedom. The guard safety test, the corner safety test and the curve test were tried and the escapement was found to be satisfactory. The banking pins were opened for slide.
Drop locks - correct.
Guard freedom - excessive.
Corner freedom - excessive.
When the guard and corner tests were tried some of the teeth would pass the locking face and come to rest on the impulse face of the pallet, that is, the safety locks did not function on some of the teeth. Since the drop locks were correct, the excessive guard and corner freedom would suggest that the error was that of a short fork. The lever was therefore stretched and the guard and corner tests were again tried. It would be well to state at this time that the stretching should be done only a very little at a time, frequently making use of the tests. It will be found that small watches need very little stretching of the lever to provide the necessary length.
Having found the guard and corner freedom correct and the safety locks satisfactory after stretching the lever, the banking pins were opened for slide.
Drop locks - deep.
Guard freedom - satisfactory.
Corner freedom - satisfactory.
The deep lock as stated above is the cause of stopping in very small wrist watches. The first act was to correct the drop locks and rebank to the drop. It was found after rebanking to the drop that the roller jewel would not pass in and out of the fork.
The roller jewel was moved a little nearer to the staff. Replacing the balance, the corner test was tried and the freedom was found to be correct, but there was no freedom between the guard pin and the edge of the roller table. This example being an escapement of the single roller type, the guard pin was bent away from the roller table. All tests were tried and found satisfactory, after which the banking pins were opened for slide.
Drop locks - light.
Guard freedom - none.
Corner freedom faulty.
Since the drop locks were light, the first act was to increase the drop locks. This made it necessary to spread the banking pins to a· new banked to the drop pas i t ion. A proper guard freedom and safety lock was found when trying the guard test, but when the corner test was tried the corner freedom was found to be excessive, and the locking was not safe on all of the teeth.
Examination showed that the roller jewel tipped slightly toward the staff. The roller jewel was reset in a position parallel with the staff and the corner test was again tried, this time showing the correct corner freedom and safety locks.
As a final check up, the several tests were tried and all were found satisfactory after which slide was added.
Drop locks - deep.
Out of Angle.
When banked to the drop the escapement showed too much guard freedom on the side of the receiving pallet and practically correct freedom on the side of the discharging pallet. to correct the deep lock and to equalize the angular motion of the lever from the line of centers, the discharging pallet was moved in. The escapement was banked to the drop and the guard test and the corner test were tried, showing too much guard and corner freedom, also a complete absence of safety lock.
The drop locks were considered passable so the error was assumed to be that of a short fork. The lever was stretched and the guard test and corner test were tried showing satisfactory freedom and safety lock.
The tests showed also that the lever's angular motion from the line of centers was equal. The ban king pins were opened for slide.
Drop locks - satisfactory.
Out of angle.
Drop and shake-close outside.
The drop locks being practically correct, the first act was to correct the condition of out of angle. As the out of angle was considerable it ,,·as necessary to move both pallet stones. The receiving pallet was moved in and the discharging pallet was moved out. After banking to the drop the balance was replaced for the purpose of finding out if the lever's angular motion was equal from the line of centers. The findings being satisfactory, the next act was to correct the drop and shake. As stated above, the condition of drop was that' of close outside. It was discovered that the pallets were so tight in the pallet arm that it was impossible to move them. The discharging pallet was therefore removed and replaced with one that was slightly thinner and the same was tipped toward the pallet arbor. This made the drop and shake equal. The several tests were tried and found satsifactory. The banking pins were open for slide.
Drop locks - correct.
Guard freedom - none.
Corner freedom - none.
After banking to the drop, this escapement did not show any guard or corner freedom. As a matter of experiment the banking pins were opened and the safety lock was found much too deep. This suggested a long fork and the correction consisted of grinding away part of the horns of the fork.
The grinding is done by placing in the lathe a small iron wire, using oil stone powder, afterwards polishing with diamantine and oil.
The ·escapement was again banked to the drop and frequent application of the safety tests were made while grinding the fork so as not to overdo the correction. The several tests soon showed the proper contact between the tooth and pallet stones. Slide was added and the watch proved to be an excellent time-keeper.
Condition of escapement - satisfactory.
Error - guard pin Jams against roller table.
This example was a single roller type escapement. After banking to the drop, the corner test was tried and found satisfactory. When the guard test was tried the guard pin would jam or stick on the edge of the roller table.
This error, responsible for frequent stopping, occurs occasionally in single roller escapements and in double roller escapements only when the guard finger is loose or bent.
The correction in the above example consisted of turning down and repolishing the edge of the roller table and advancing the guard pin. In the above problems frequent use of the expression 'banked to drop' is made. We are very well aware of the fact that it is impractical to bank to the drop the escapement in those watches that do not have adjustable banking screws. In such cases we have to take note of the position of the lever when the drop takes place and determine as best we can the amount of slide that remains.